The densification mechanism during the park-plasma-sintering (SPS) processing was
examined in high purity MgAl2O4 spinel. As the density ρt increases, that is, as the effective stress σeff
decreases, stress exponent n evaluated from σeff dependence of densification rate varies from n ≥ 4 in
the low ρt region, n ≈ 2 in the intermediate ρt region to n ≈ 1 in the high ρt region. TEM observation
shows that significant stacking faults caused by partial dislocations are observed in the low ρt region,
but limited in the high ρt region. The ρt dependent densification behavior and microstructure suggest
that the predominant densification mechanism during the SPS processing changes with ρt from plastic
flow by partial dislocation motion for the low ρt region (n ≥ 4) to diffusion-related creep for the high
ρt region (n ≈ 1).